Method for machining spaced surfaces

ABSTRACT

The method for finish machining parallel surfaces on a workpiece in which the machine tools which are movable across the surfaces to be machined are mounted on relatively movable supporting head sections. The tools are moved radially inwardly along opposite surfaces of a rotating workpiece, one of the head sections is then moved a predetermined distance in a direction to move the tool thereon away from the tool on the other head section, the workpiece is then moved in the same direction a smaller distance so that both surfaces are spaced from the tools, and the head is then retracted while the tools are spaced from the workpiece surfaces to positively preclude the formation of objectionable drawback lines on the workpieces.

United States Patent Skrentner 51 June 20, 1972 METHOD FOR MACHINING SPACED SURFACES Inventor: Frank C. Slu'entner, Bloomfield Hills,

Mich.

Assignee: LaSalie Machine Tool, Inc., Warren, Mich. Filed: March 29,1971

Appl. No.: 128,818

Related US. Application Data Division of Ser. No. 833,349, June 16, 1969, Pat. No. 3,592,089.

u.s. c1. ..82/1 c, 82/24A Int. Cl. ..B23b 1/00 ma oiSeareh ..82/1 (2, 2 A, 24 A, 4 A

References Cited UNITED STATES PATENTS lO/ 1 950 Garrand ..82/24 A 2,734,255 2/1956 Tack.. ..82/4A 3,442,164 5/1969 Blazer ..82/2A Primary Examiner-Leonidas Vlachos Attorney-Olsen and Stephenson [57] ABSTRACT The method for finish machining parallel surfaces on a workpiece in which the machine tools which are movable across the surfaces to be machined are mounted on relatively movable supporting head sections. The tools are moved radially inwardly along opposite surfaces of a rotating workpiece, one of the head sections is then moved a predetermined distance in a direction to move the tool thereon away from the tool on the other head section, the workpiece is then moved in the same direction a smaller distance so that both surfaces are spaced from the tools, and the head is then retracted while the tools are spaced from the workpiece surfaces to positively preclude the formation of objectionable drawback lines on the workpieces.

2 Claims, 6 Drawing Figures PATENTEDmzo m2 SHEET 1 BF 3 INVENTOR FRANK C.SKRENTNER a4 bu/Mm,

ATTORNEYS PATENTEDJum [s72 SHEET 2 OF 3 INVENTOR I FRANK C.SKRENTNER ATTORNEYS PATENTEnJum 1912 3,670,607

sum sur 3 INVENTOR FRANK CLSKRENTNER wAfidw/gazw ATTORNEYS METHOD FOR MACHINING SPACED SURFACES CROSS REFERENCE TO RELATED APPLICATION This application is a division of copending application Ser. No. 833,349 filed June 16, 1969 now U.S. Pat. No. 3,592,089.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION The method of this invention is particularly adapted for finish facing parallel surfaces on disc brake rotors, and is particularly described herein with reference to this specific application, although it is to be understood that the method of this invention is not limited to this single application. Pat. applica tion Ser. No. 792,100 filed Jan. 17, 1969, now U.S. Pat. No. 3,593,064 and assigned to the assignee of this application discloses an indexable turret head tool support in which a series of tools are sequentially usable, on indexing of the head, so that it is not necessary to shut down the automated line carrying parts to be machined each time a set of tools has become worn. The method of this invention provides for relative movement of parts of the turret head which machine oppositely facing surfaces on the workpiece, thereby enabling spacing of the tools from the workpiece surfaces during retracting of the tools. More specifically, following machining of the workpiece surfaces, one of the head sections is moved a predetermined distance in a direction away from the surface which it has just completed machining. The workpiece is then moved in the same direction a distance less than this predetermined distance to thereby provide for all of the tools being spaced from the surfaces which they have just finished machining. The tools are then retracted, and because they are spaced from the machined surfaces, the possibility of the tools forrning objectionable drawback lines on the machined surfaces is positively precluded. An air chamber is formed in the turret head so that when air is supplied thereto, the tool sections are moved to position the tools thereon for machining a workpiece. When the supply of air to the air chamber is discontinued, springs in the turret head are capable of moving one of the tool head sections the predetermined distance described above. An air passage system is also included in the turret head for signaling the position of the movable turret head section.

Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims, and the accompanying drawing in which:

FIG. 1 is a fragmentary sectional view of the turret head of this invention, showing the turret head sections in position for machining a workpiece, and illustrating a workpiece in a position to be machined by tools on the turret head;

FIG. 2 is a sectional view like FIG. 1 showing the turret head and the workpiece in position following completion of the movement of the turret head to machine the workpiece; and

FIGS. 3, 4, 5 and 6 are diagrammatic views illustrating the steps in the method of this invention which follow movement of the turret head to the position shown in FIG. 2.

With reference to the drawing, the method of this invention utilizes machining apparatus indicated generally at 10 in FIG. 1, which includes a turret head 12 constructed generally like the turret head described in the aforementioned copending application except that the present turret head 12 includes what is termed herein a fixed section 14 and a movable section 16. During use of the turret head 12, the fixed section 14 remains in a fixed position relative to a spindle 18 on which the head 12 is mounted and the movable section 16 is movable back and forth axially of the spindle 18. A body 20 supports the spindle 18 in a manner described in detail in the aforementioned copending application.

A plurality of workpieces 22, only one of which appears in FIG. 1, are mounted on fixturing and indexing apparatus 24, the details of which form no part of the present invention, which is capable of both rotating the workpiece 22 about its axis which is parallel to the axis of spindle l8 and of advancing the workpiece 22 in a direction parallel to the axis of spindle 18. In the illustrated embodiment of the invention, the workpiece 22 is a disc brake rotor having parallel surfaces 26, 28 and 30 which it is desired to finish face by use of the turret head 12. It should be noted that the: surface 26 faces in one direction and the surfaces 28 and 30 face in an opposite direction.

The fixed turret head section 14 is generally cylindrical in shape having an annular gap or groove 31 intermediate its ends, and the movable section 16 is positioned generally within this groove 31. A plurality of cutting tools 32, only one of which is shown, are mounted on the turret section 16 so that the head 12 can be indexed through predetermined angular increments about the axis of the spindle 18 to successively move each of the tools 32 into operative position, as explained in detail in the aforementioned copending application. A similar set of cutting tools 34, only one of which is shown, are mounted on the turret head section 14 at positions aligned axially with the tools 32. A third set of tools 36 is mounted on the head section 14 in a predetermined spaced relation with the tools 34. In the position of the head section 16 illustrated in FIG. 1, the tools 32, 34 and 36 are spaced apart distances corresponding to the desired spacing of theworkpiece surfaces 26, 28 and 30. As a result, when the workpiece 22 is moved to the position shown in FIG. 1 in which the surfaces 26, 28 and 30 are substantially aligned with the tools 32, 34 and 36, respectively, the head 12 is movable toward the workpiece 22, which is being rotated at this time, to the position shown in FIG. 2 to finish face the surfaces 26, 28 and 30.

As shown in FIG. 1, the turret head section 16 is of annular shape and is supported at its radially inner side on a tubular portion 38 of the head section 14. A plurality of springs 40, mounted on the head section 14 and engaged with the head section 16 continually urge the head section 16 in a direction tending to move the tools 32 away from the tools 34 and 36. Guide pins 42, only one of which is shown, on the head section 16 extend into guide passages 44formed in the head section 14 so as to guide the head section 16 during movement relative to the head section 14.

An air passage 46 in the spindle 18 communicates with an air chamber 48 in the head 12, one wall 50 of which is formed by the head section 16. On supply of air to the chamber 48, the head section 16 is urged against the pressure of the springs 40 in a direction to move the tools 32 toward the tools 34. Such movement is limited by engagement of a surface 52 on section 16 with a surface 54 on the head section 14. When the surfaces 52 and 54 engage, the tools 32 are in a precisely spaced relation relative to the tools 34 corresponding exactly to the desired spacing of the workpiece surfaces 26 and 28. When the supply of air to the chamber 48 is discontinued, and the passage 46 is connected to atmosphere, the total air pressure force on the section surface 50 quickly drops below the force of the springs 40 on the section 16, resulting in movement of the section 16 to a position in which the surface 50 engages projections 56 on the head section 14, the purpose of which is to prevent elimination of the chamber 48 when the head section 16 is moved to this position. In this position of the head section 16, the spacing between the tools 32 and 34 is increased, for a purpose to appear presently.

In the operation of the machining apparatus 10, assume that the head 12 is in the position illustrated in FIG. 1, the workpiece 22 is also in the position shown in FIG. 1, and it is desired to finish face the workpiece surfaces 26, 28 and 30. The workpiece 22 is rotated and the turret head 12 is moved toward the workpiece 22 so that the tools 32, 34 and 36 are moved radially inwardly on the workpiece surfaces 26, 28 and air from the chamber 48. This allows the springs 40 to move the head section 16 in a direction to move the tools 32 a predetermined distance away from the tools 34, as shown in FIG. 3. The workpiece rotating and indexing mechanism 24 is then operated to move the workpiece 22 in a direction toward the tools 32 a distance less than the distance the tools 32 have just been moved away from the tools 34 to thereby place the workpiece 22 in the position shown in FIG. 4. As shown in FIG. 4, the workpiece surfaces 26, 28 and 30 which have just been finish faced are now spaced from the tools 32, 34 and 36, so that the head 12 can be moved to the retracted position shown in FIG. 5. Air under pressure is then resupplied to the passage 46 so that the air under pressure in the chamber 48 will move the head section 16 in a direction to compress the springs 40 and move the tools 32 into the predetermined spaced relation with the tools 34 illustrated in FIG. 1 and in FIG. 6. The apparatus 24 is then operated to move the workpiece 22 which has just had the surfaces 26, 28 and 30 finish faced out of an aligned position with the head 12 and move the next successive workpiece 22 to the position illustrated in FIG. 6 in which the surfaces 26, 28 .and 30 thereon are substantially aligned with the tools 32, 34 and 36. The abovedescribed cycle is then repeated to provide for finish facing of the surfaces 32, 34 and 36 on the workpiece 22 which is aligned with the head 12 to provide for the finish facing of these surfaces.

A second air passage 60 in the spindle 18 communicates continually with a passage 62 in the fixed head section 14. A

LII

flange 64 on movable head section 16 has a through passage 66 formed therein which lines up with the passage 62 when the tools 32 are in a machining position (FIG. 1). However, when the head section 16 has been moved to the inoperative position (FIG. 3) the passage 66 is out of alignment with passage 62 so that passage 62 is blocked by flange 64 causing back pressure in passage 60. This back pressure is useful in connection with conventional pressure responsive valve and switch apparatus to signal the position of head section 16 during automatic operation of head 12.

From the above description it is seen that this invention provides a method for finish facing parallel surfaces on a work piece without any possibility of forming undesirable drawback lines on the surfaces. This enables inclusion of the head 12 in automated machinery capable of rapidly finish facing surfaces such as the ones illustrated at 26, 28 and 30 on the illustrated disc brake rotor 22.

What is claimed is:

1. The method for machining substantially parallel spaced surfaces on a workpiece without forming drawback lines on said surfaces comprising the steps of:

a. engaging said surfaces with tools which are spaced apart a distance corresponding to the spacing of said surfaces;

b. advancing said tools along said surfaces to accomplish machining thereof;

c. moving one of said tools in a direction away from the other one of said tools a predetermined distance;

d. moving the workpiece in said direction a distance less than said predetermined distance to a position in which said surfaces are spaced from said tools; and

e. retracting said tools.

2. The method according to claim 1 wherein said workpiece is of an annular shape and said surfaces form opposite faces thereof and wherein said tools are moved radially inwardly on said faces during advance thereof. 

1. The method for machining substantially parallel spaced surfaces on a workpiece without forming drawback lines on said surfaces comprising the steps of: a. engaging said surfaces with tools which are spaced apart a distance corresponding to the spacing of said surfaces; b. advancing said tools along said surfaces to accomplish machining thereof; c. moving one of said tools in a direction away from the other one of said tools a predetermined distance; d. moving the workpiece in said direction a distance less than said predetermined distance to a position in which said surfaces are spaced from said tools; and e. retracting said tools.
 2. The method according to claim 1 wherein said workpiece is of an annular shape and said surfaces form opposite faces thereof and wherein said tools are moved radially inwardly on said faces during advance thereof. 